Project Summary/Abstract The incidence of pancreatic cancer has increased at an alarming rate in recent years. Due to the insidious and aggressive nature of the disease, at the time of presentation more than 90% of patients have local or metastatic spread precluding curative resection. Thus, a critical requirement for progress will be the development of new and effective therapeutic modalities for pancreatic cancer. Improvements in diagnostic tools to facilitate the staging of cancer will be expected to advance the progress of treatment and optimize management of the disease. The employment of conditionally replicative adenoviruses (CRAds) constitutes a promising alternative for cancer treatment. In this proposal, we combine the advantages of the antitumor effect of infectivity enhanced CRAds, radioiodine therapy, and noninvasive radionuclide-based imaging to develop a novel approach for pancreatic cancer treatment and detection of peritoneal metastases. The proposed research involves production of an entirely new generation of CRAd constructs expressing a therapeutic and imaging transgene, the human sodium-iodide symporter (NIS), which will induce uptake of radioactive iodine by tumor cells. NIS expression will allow noninvasive staging of the disease through visualization of adenoviral replication, but more importantly, will allow therapy with radioiodine 131I similar to that practiced clinically with high efficacy for metastatic thyroid cancer. The structure of our CRAd is designed to overcome low efficacy of current vectors and make them practical for systemic administration. Adenovirus replication will occur exclusively in tumors through the inclusion of a tumor specific promoter allowing specific delivery of critical viral genes. Adenovirus hexon modification will further reduce liver sequestration. Combination with radiotherapy will synergistically enhance the effect of viral oncolysis. Noninvasive imaging of viral replication will provide both detection of metastases and CRAd biodistribution information. To mimic human metastatic disease, a pancreatic cancer model induced by either orthotopic or intraperitoneal tumor inoculation will be used with vectors delivered via systemic and intraperitoneal routes. In addition to a nude mouse model, an immunocompetent syngeneic hamster model, which permits human adenovirus replication, will be tested to analyze the efficacy and safety of CRAd-based radioiodine therapy and imaging. A multimodal therapy with high clinical potential that combines oncolytic viral therapy, radioiodine therapy, and imaging techniques can be developed for pancreatic cancer patients based on this novel approach. Successful products from this proposal can be promptly translated to the clinical arena bringing novel and effective therapies to the patients with pancreatic cancer including those with unresectable tumors.